Organic growth on your roof is more than a cosmetic issue. Moss, algae, and lichen retain moisture against roofing materials, accelerating deterioration and shortening the lifespan of shingles, slate, and tile. Addressing these growths promptly protects your investment.
How Organic Growth Damages Roofing Materials
Moss and lichen root into the surface of asphalt shingles and natural slate, lifting edges and creating channels where water can penetrate beneath the roofing material. As these organisms expand, they trap moisture against the roof surface, preventing it from drying properly. In freezing temperatures, that trapped moisture expands, causing micro-fractures in slate and tile and granule loss in asphalt shingles.
Identifying the Type of Growth on Your Roof
Black streaks are typically caused by gloeocapsa magma, a type of algae that feeds on the limestone filler in asphalt shingles. Moss appears as green, fuzzy patches, usually in shaded areas or on north-facing roof slopes. Lichen presents as flat, crusty patches in gray, green, or yellow tones. Each requires a different treatment approach for safe and effective removal.
Professional Soft-Wash Roof Cleaning
Hoover Roofing uses low-pressure soft-wash techniques that eliminate organic growth without damaging roofing materials. High-pressure washing can strip granules from shingles and crack slate, so we rely on specialized cleaning solutions that kill organisms at the root and prevent rapid regrowth. This method is safe for asphalt shingles, slate, tile, and metal roofing.
Preventing Future Growth
After cleaning, we recommend trimming overhanging tree branches to increase sunlight and airflow across the roof surface. Installing zinc or copper strips near the roof ridge can also inhibit future growth, as rainwater washes trace amounts of metal ions down the roof slope. Regular inspections help catch new growth before it becomes established.
Key Takeaway
Never pressure wash a roof. Professional soft-wash treatment eliminates organic growth safely without stripping granules or cracking slate and tile.